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Advantages Main Memory Has Over Magnetic Disk Storage

by Isaiah David

Most of the memory used in a typical computer falls into two categories: RAM and hard-drive memory. RAM, sometimes called main memory, is stored in computer chips using a grid of tiny switches. Hard-drive memory involves storing data as tiny magnetic signatures on a spinning disk. Both forms of memory are important to a computer's operation, and each has its own advantages and disadvantages.

Overview

Most of the memory used in a typical computer falls into two categories: RAM and hard-drive memory. RAM, sometimes called main memory, is stored in computer chips using a grid of tiny switches. Hard-drive memory involves storing data as tiny magnetic signatures on a spinning disk. Both forms of memory are important to a computer's operation, and each has its own advantages and disadvantages.

Speed

Main memory is far faster than magnetic disk storage. When the computer wants to access a sector on the hard drive, it must spin up the disk, move a read/write arm to the right spot on the drive and read the information as the disk spins. To read a section of the RAM, the computer only has to send a signal to the word line and bit line (the two wires that give the location of a particular piece of data) and read the resulting information. Because main memory is so much faster than magnetic disk storage, computers perform as many of their calculations as possible in main memory and save the secondary storage for more permanent information.

No Moving Parts

Magnetic disk storage has gotten better over the years, but it is still vulnerable to mechanical failure. A hard drive has moving parts that can either wear out gradually or abruptly "crash." A hard-drive crash is sometimes just that: The arm holding the read-write head can collide with the surface of the drive, digging a big hole in it and destroying large swaths of data. Alternatively, the magnetic coating on small sections of the drive can erode, or the spindle or other moving parts can start to wear out. Main memory devices, which have no moving parts, are very robust and rarely wear out from normal usage.

Ease of Replacement

Main memory and magnetic disk storage serve quite different purposes. Magnetic disk storage holds permanent or semipermanent information, whereas main memory only keeps track of the info the computer needs when it is running. Because of this, main memory is far easier to replace than magnetic disk storage. Even novice computer users can replace a RAM chip by pulling out the old one and sticking a new one into the same slot. To replace a hard disk, by contrast, you must back up all your files before you can even take the physical drive out. You then must reinstall and reconfigure many of your programs once you get the new drive up and running.

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